The physiology and biochemistry of adrenarche.

Adrenarche refers to the rise in adrenal 19- carbon steroid production, primarily dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEAS). Adrenarche, which occurs only in humans and a few higher primates, is independent of puberty and manifests clinically as the appearance of axillary and pubic hair, usually about age 8. The physiologic correlate of adrenarche is the development of the adrenal zona reticularis, which has many of the biochemical properties of the fetal adrenal. Recent studies have shown that adrenarche is not an abrupt and 'signaled' process occurring in mid childhood but rather a continuous process since birth. In addition, some differences in gene expression between the zona reticularis and the fetal adrenal gland have begun to emerge. The purpose of adrenarche in human physiology remains enigmatic, although disease states associated with abnormalities in DHEA(S) production provide some clues.